- Go to the MODIS Rapid Response Image Gallery and enter Aral Sea in the Search field. Browse through the images and come up with your own research question about how the Aral Sea region has changed over time. Use the techniques in this chapter to quantify your study.
- Search the MODIS Rapid Response Image Gallery for images of the Aral Sea and try to pinpoint the date that the former island (named Vozrozhdeniye, which means "renaissance" or "rebirth") between the east and west portions of the sea became a peninsula of the mainland. Consider the implications for biodiversity for an island that becomes part of the mainland: for instance, are island species likely to spread to the mainland or will they become prey to mainland predators that now have access to them?
- Search for and download other images of the Aral Sea from MODIS and Landsat. Use a combination of techniques from this chapter to construct a more detailed record of how the area of the sea has changed over time.
The process of setting a scale and making measurements from images is the same for any image in which the features appear in the same focal plane. Thus, the techniques can be applied to any satellite image produced with a nadir (straight down) orientation, regardless of what parameter it measures or if the image is displayed in true or false colors. Additionally, this technique would work just as well for microscopic images as for satellite images. Five sites of special interest to this chapter are noted below.
Aral Sea Image of the Day has a set of images one is from 1989.
World of Change Aral Sea shows a series of images of the Aral Sea from 2000 to present. These images can be downloaded and analyzed in ImageJ.
A reference article The Shrinking Aral Sea also has images to use.
EarthShots: Satellite Images of Environmental Change is a collection of registered time series images taken by Landsat instruments since 1972. You can use the same techniques presented in this chapter to set a scale and measure distances and areas in this collection of images.
Search on NASA Earth Observatory for the phrase time series to find "before and after" images. Set a scale for each image and make measurements to give a quantitative description of the change that occurred.
The NASA Earth Observatory: World of Change features many other sets of images that would be appropriate to use with the techniques described in this chapter.
Occasionally, you may find an image that you would like to make measurements from, but its spatial resolution is not stated clearly. Here are some techniques you might use to set the scale for such an image.
- If the image contains a graphic distance scale, select a straight line along it, then choose Analyze > Set Scale... and enter the Known Distance indicated by the scale.
- If you can identify two specific features in the image, select a line between the two points then choose Analyze > Set Scale.... Find the Known Distance between the locations (by measuring it in an atlas, or with Google Earth, for example) and enter it along with the appropriate units of length.
- If you know the satellite instrument that recorded the image data, visit the instrument's website. Many instruments record data at a constant resolution or their data products are prepared at specific resolutions.
- You can occasionally open image files into a text editor application, and read recognizable header information that states the spatial resolution.
- Submit feedback to data sites, asking them to specifically state image resolutions.
Case Studies with Tool
Other EET chapters that utilize ImageJ as a tool and satellite imagery as a data source include the following:
Using NASA NEO and ImageJ to Explore the Role of Snow Cover in Shaping ClimateInvestigate satellite images displaying land surface temperature, snow cover, and reflected short wave radiation data from the NASA Earth Observation (NEO) website. Animate the images and compare them with the NEO ICE tool.
Using Satellite Images to Understand Earth's AtmosphereUse ImageJ to create an animation showing the change in monthly concentration of aerosols over the course of a year and compare it to a similar animation showing change in carbon monoxide concentration.
Annotating Change in Satellite ImagesUse time-series images to produce a map documenting land-use changes in China.
Analyzing the Antarctic Ozone HoleMeasure and graph the area of depleted ozone from Total Ozone Mapping Spectrometer (TOMS) images.
Exploring and Animating GOES ImagesTransform a time series of GOES images into an animation. Plot a storm track and determine storm speed.
Shrinking Forest - Growing ProblemUse time-series Synthetic Aperture Radar (SAR) images to create a color composite image showing the oldest to most recently deforested areas in the Amazon rainforest.
Whither Arctic Sea Ice?Animate thirty years of sea ice images, measure the ice extent each year, and then graph and analyze the results.